In a single-phase power supply system, single-phase three-wire power distribution is usually effectuated with a single-phase transformer disposed on a second-order routing side and characterized by a center tap structure. In event of load unbalance, the aforesaid power distribution is predisposed to voltage unbalanced, transformer saturation and overheating. To prevent the aforesaid problems, it is necessary to limit the extent of load unbalance at the expense of power supply level. To overcome the aforesaid drawback of the prior art, it is important to compensate for unbalanced current in the presence of load unbalance with a view to maintaining the initial system power supply level; to this end, a single-phase three-wire inverter is used to not only effectuate the compensation but also dispense with a transformer. Furthermore, past research about single-phase three-wire inverter circuits mainly focuses on three-leg switching control and requires a control framework whereby a single-phase three-wire system is decoupled to enable common-mode and different mode systems for control purposes, that is, turning the systems into one 220V system and two 110V systems, and the control of the two 110V systems is rendered decoupled. The aforesaid control techniques are complicated, and the central leg of the inverter circuit must be series-connected to a filter inductor, thereby adding to the system construction cost and volume.